Explosion-proof Electric Heater
An explosion-proof electric heater is an electric heating device specifically designed for flammable and explosive hazardous environments. Through special structural design, it ensures safe operation in explosive gas or dust atmospheres. It is widely used in high-risk places such as chemical industry, petroleum, natural gas, military, shipbuilding, and mining areas, and is an indispensable key equipment for industrial safety production.
Working Principle
The explosion-proof electric heater operates based on the current thermal effect (Joule heating): low-temperature fluid media enters the heater inlet under pressure, flows along the internal specific heat exchange flow channels, carries away the high-temperature heat energy generated by the electric heating elements, and after the medium temperature rises, it is discharged from the outlet, achieving the temperature required by the process.
Its explosion-proof core principle lies in the special structural design:
Flameproof enclosure: The junction box and control parts adopt a flameproof enclosure made of cast aluminum alloy (such as ZL102), which can withstand internal explosion pressure and prevent flame from spreading outward
Overheat protection: An independent overheat protection device immediately cuts off the power supply when the heating element overheats, preventing material coking, carbonization, or element burnout
Interlock control: It can be interlocked with parameters such as pressure and flow, and cooperate with the DCS system to achieve fully automated operation and remote monitoring
The explosion-proof level of the explosion-proof electric heater directly determines its applicable places, and it must strictly match the classification of the hazardous area on site:
Interpretation of Explosion-proof Markings
Table
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Marking Meaning
Ex d ⅡB T4 Gb Flameproof type, suitable for ⅡB class gas environments, temperature class T4 (maximum surface temperature ≤135℃), equipment protection level Gb
Ex d ⅡC T4 Gb Flameproof type, suitable for ⅡC class gas environments (hydrogen and other most dangerous gases), temperature class T4
Ex tD A21 IP66 T130℃ Suitable for combustible dust environments Zone 21, protection level IP66, maximum surface temperature 130℃
Applicable Hazardous Areas
Gas environments: Zone 1, Zone 2; ⅡA, ⅡB, ⅡC class explosive gases; temperature classes T1 to T4
Dust environments: Zone 21, Zone 22 combustible dust places
Main Implementation Standards
GB 3836 series: General requirements for electrical equipment for explosive atmospheres (core standard)
GB/T 34663-2017: General technical requirements for resistance heaters for explosive gas atmospheres
GB 3836.15-2024: Selection and installation standard
IEC 60079 / ATEX / IECEx: International explosion-proof certifications
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Parameter Typical Range
Rated voltage 220V / 380V / 460V / 660V / 1140V
Rated power 1kW to 3000kW
Maximum working temperature 720℃ (some models can reach 850℃)
Temperature control accuracy ±0.2℃
Thermal efficiency Close to 100% (99% of heat transferred to the medium)
Pressure resistance Up to 20MPa
Protection level IP66
Explosion-proof marking Ex d ⅡB/ⅡC T4 Gb
Power density 0.8 to 15 W/cm² (depending on the medium)
Heating tube material Stainless steel 304/316L, carbon steel, titanium alloy
Shell material Cast aluminum alloy ZL102
By Structural Form
Flange-type explosion-proof electric heater: Installed on the container wall via flange, suitable for heating liquids in containers such as water tanks, oil tanks, reaction towers, and storage tanks
Immersion-type explosion-proof electric heater: Heating elements are directly immersed in the medium, suitable for oil tanks and chemical storage tanks
Circulation/duct-type explosion-proof electric heater: The medium circulates and flows in a closed pipeline for heating, suitable for continuous heating conditions such as gases and heat transfer oil
Storage tank-type explosion-proof electric heater: Specially designed for large storage tanks, adopting a flexible structure, allowing bending and replacement of heating elements without draining the tank
Suction-type explosion-proof electric heater: Suitable for heating and conveying high-viscosity media
By Heating Principle
Resistance wire type: Nickel-chromium alloy wire heating, traditional and mature, wide applicable temperature range
PTC ceramic type: Positive temperature coefficient self-limiting temperature, no open flame, no red glow, extremely high safety, voltage range 12V to 380V, can be used continuously for more than 10 years
Far-infrared type: Radiant heating, suitable for large containers such as reactors and pipelines
Petrochemical industry: Heating of hydrocarbons such as crude oil, heavy oil, fuel oil, heat transfer oil, lubricating oil, and paraffin; material temperature rise, powder drying
Natural gas: Natural gas preheating, dehydration, and desulfurization process heating
Marine and ocean engineering: Heating of engine rooms, oil tanks, pump rooms, chemical tanks, and inert gas systems; fuel/lubricating oil preheating, cargo oil tank insulation; must meet classification society certifications such as CCS, DNV, LR
Military and national defense: Heating in high-risk places such as ammunition depots and pyrotechnic workshops
Mining areas: Ventilation heating in coal mines, heat tracing for gas drainage pipelines
Pharmaceutical and food: Process fluid heating in clean environments
New energy: Temperature control in lithium battery production lines, heating for photovoltaic polysilicon
Explosion-proof level matching: Select the corresponding explosion-proof marking according to the classification of the hazardous area on site (Zone 1/Zone 2, ⅡA/ⅡB/ⅡC, T1 to T4), and must obtain the complete machine explosion-proof certificate
Confirmation of heating medium: Different media (water, oil, heat transfer oil, gas, molten salt) have different requirements for material, power density, and surface temperature
Power calculation: Calculate the required power comprehensively based on medium volume, heating rate, insulation needs, and heat loss
Material selection: For corrosive media, choose stainless steel 316L or titanium alloy; for high-temperature conditions, choose Incoloy alloy
Temperature control method: Whether DCS remote temperature control, multi-stage temperature control, over-temperature/low liquid level/overpressure interlock protection are needed
Installation method: Flange connection, threaded connection, or welding; confirm the container interface size and installation space
Special certifications: For marine use, classification society certification is required; for export, ATEX/IECEx international certification is required
Must be used with temperature control interlock: The explosion-proof electric heater is an explosion-proof component and must be used in conjunction with temperature interlock control protection devices such as thermocouples; naked use is strictly prohibited
Heating section immersion requirement: The heating tube within 100mm from the flange surface is the non-heating part; during use, the heating part must be immersed in the medium by more than 50mm
Dry burning strictly prohibited: The immersion heater must be powered off after the medium is drained
Regular inspection: Check the integrity of the flameproof surface, aging of seals, and grounding reliability
Maintenance specifications: When replacing heating elements, power must be cut off and confirm there is no residual explosive gas
Installation grounding: The equipment shell must be reliably grounded, and the grounding resistance must meet requirements
